There are 3rd party chromatic aberration filters you can get or you can simply scale the red, green and blue channel of an image by slightly different amounts yourself.

The plugin just saves you a little time because manually you'll need to do something like copy your clip three times, in each one shuffle the red into all channels, another the green into all channels and so on, or better yet, shuffle black into the green and blue of the red layer, black into the red and blue of the green layer, and so on. It all depends on how your software works and how easiest to recombine the layers once you're done.

Then you scale one or two of them non-uniformly, so maybe make the red layer slightly larger and the blue layer slightly smaller, but just in the horizontal or X direction.

Then ADD all three layers together or shuffle a channel from each into a new fourth layer. It all depends on what software you're using.